code: def _identity(x):
      return x
  
file_path: advertorch/tests/test_bpda.py
imports: import itertools
  import pytest
  import torch
  import torch.nn
  from advertorch.bpda import BPDAWrapper
  from advertorch.utils import torch_allclose
  from advertorch.test_utils import withgrad_defenses
  from advertorch.test_utils import nograd_defenses
  from advertorch.test_utils import defense_kwargs
  from advertorch.test_utils import defense_data
  from advertorch.test_utils import vecdata
label_desc: Use image node_id 1 for calling a global function with example usage: _identity(x) and returns: x